The growing availability of digital technology is having an impact on medical imaging practice. Image archiving and communications systems allow for digital acquisition, image processing and display for a wide variety of medical imaging modalities in a digital environment. Digital medical imaging has led to an increase in productivity for the health care professionals who need to utilize images as part of patient care. To maintain this high productivity it is important for the health professional to extract diagnostically useful information from the medical images at a digital display. Digital displays have many advantages over film such as a wide variety of tools to manipulate and process the image to enhance structures or make them more visible. Yet another advantage is the availability of tools to segment images, detect, and classify lesions and to make comparisons with previous images that can be viewed from imaging archives. Chiefly due to these tools, the radiologist now has a considerable amount of influence over the quality of the image. While overall enhancing quality assurance (QA) it has led to variability in how perception and observer performance affects the quality assurance process because a completely new array of considerations arises. There are significant variations in a general image appearance with different anatomies, views, and x-ray image acquisitions.
For a radiologist, the acquired digital x-ray image may not be always satisfactory from a diagnostic point of view. Some of the image areas may be too dark, or there may be insufficient contrast in the regions of interest. Fortunately, with digital radiography it is possible to adjust the image brightness and contrast of the image by adjusting the window level (WL) and the window width (WW) of the image. However, WL and WW adjustments need to be such that overall brightness and contrast are consistent from one image to the next for a given set of conditions. The WL and WW adjustment issue is further complicated by the fact that each user has a personal preference of the consistent appearance.
Diagnostic accuracy is certainly the major consideration, but a good quality assurance system can affect observer performance in other ways. Workflow or the amount of time the radiologist spends on an individual image can easily be regarded as a reflection of the quality assurance process. If the display is inadequate in some way, it is quite likely that the radiologist will have to compensate by taking more time to examine the image before rendering a diagnostic decision. When radiographic images are viewed with electronic displays, adjustment of window width and level is a standard practice used to improve the rendering of a region-of-interest. Adjustment of window width and level is most often done manually, most often using a mouse or track-ball, and requires substantial time and effort to obtain a desired result. Window width and level adjustment requires a skilled operator to be accomplished successfully. Further, adjusting window width and level for a region of interest often has the effect of making the remaining areas of the image sub-optimally rendered. In addition to this loss of image quality, adjusting window width and level can also cause a loss of context for the region of interest leading to some areas being under expose while other areas are overexposed.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for automating the selection of window width and window level with minimal user interaction. There is also a need in the art for electronic displays to provide consistent brightness and contrast settings for a set of images.